In the conventional electronically controlled fuel injection pump for an internal combustion engine, in order to obtain desired governor characteristics, the optimum position of an adjusting member for adjusting the amount of fuel injected at any time is computed on the basis of input data indicative of the conditions of engine operation such as engine speed, amount of manipulation of the accelerator pedal etc., and the adjusting member is controlled by an actuator so as to be positioned at the optimum position in accordance with the computed result. In such a control system for a fuel injection pump, in order to avoid problems caused by excessive supply of fuel, such as the production of smoke due to imperfect fuel combustion, there is provided a circuit for limiting fuel injection in such a way that the amount of fuel injected is not more than a maximum value represented by a characteristic signal determined from a characteristic curve for the maximum amount of fuel to be injected, which is produced by a characteristic signal generator.
The characteristic curve for the maximum amount of fuel to be injected (referred to as a "full Q characteristic curve" hereinafter) must be decided so as to match the characteristics of the engine equipped with the fuel injection pump. For critically adjusting the full Q characteristic curve to the best condition, it is necessary to carry out adjustment of the characteristic curve under the actual operating condition of the fuel injection pump separately for each engine.
Therefore, the conventional electronically controlled fuel injection pump is arranged so as to be adjustable in its full Q characteristics. The full Q characteristics are a function of engine speed and are quite complex. The conventional device is arranged so that the full Q values are represented by a broken line curve and each segment of the broken line is adjusted in its positional level and/or its slope by the adjustment of variable resistors. Much time and skill are required for the adjusting operation. Consequently, it is difficult to reduce the cost for adjustment of the device and the adjusting operation is also inconvenient when carrying out an engine test.